The extracellular deposition of amyloid B protein in cores of neuritic plaques and walls of blood vessels in brains and leptomeninges is a neuropathological hallmark of aging, Alzheimers disease (AD), Down syndrome, and hereditary cerebral hemorrhage with amyloidosis (Dutch type). The identification of the amyloid beta protein precursor (APP) gene, its localization to human chromosome 21, and its expression in various tissues and cell types presents an opportunity to determine the pathological process leading to the formation of amyloid beta protein. The APP gene has a complex transcriptional unit with two polyadenylation sites. It encodes multiple transcripts for a family of secreted proteins. One of these proteins is protease nexin II, which inhibits certain serine proteases. The APP gene is differentially expressed in all major tissues. In brain it is expressed primarily, but not exclusively, in neurons. The apparent overexpression of the APP gene in Down syndrome and in certain areas of the brain of AD patients indicates a possibility that this overexpression might be a critical requirement for AD neuropathology and is probably an indicator of a much broader abnormality in gene regulation for the disease. The goals of this project are designed to study regulatory mechanisms of transcription responsible for the control of the APP gene expression and to identify factors that are responsible for abnormal regulation of the APP gene expression in aging and in Alzheimers disease. We will use recombinant DNA clones and DNA sequence information already available to identify regulatory sequences in the APP promoter, and to discover putative regulatory factors that bind to the promoter of the APP gene. To accomplish this, we propose to locate the major block of regulatory elements of the APP gene and to establish its 5' and 3' boundaries. We will demonstrate that these sequences are sufficient to specify the APP gene expression in different cell types by investigating the expression of hybrid genes containing these regulatory elements linked to simple reporter genes. We will identify component sequence motifs within the promoter that are important for differential expression of the APP gene. Next, we will identify nuclear factors that bind to these regulatory elements. We will als identify factors, or mediators, that can modulate the expression of the APP gene. APP gene products ar essential for cell growth and at least one of these product, protease nexin II, inhibits epidermal growth factor binding protein and gamma subunit of nerve growth factor. The major focus of this part of the project will be on the ability of different factors to modulate the expression of the APP gene. The expression of these modulators of the APP gene in aged human brain and in Alzheimers disease will help in the understanding of both the aging process and the disease.